An oil-based ballpoint pen generates a so-called dripping phenomenon by causing ink to leak out from the tip end, due to its simple structure, or a blobbing phenomenon of extended wetting to the tip or soiling the paper surface and these problems have been conventionally overcome by adjusting the ink viscosity to about 10,000 mPa·s, limiting the ink outflow mechanism in terms of the design of structure such as inner diameter of ink reservoir tube or clearance at the pen tip, imparting thixotropy, for example, by the addition of an inorganic filler particle to the ink, or adding a specific polymer, and thereby affecting the ink ejection. However, the ink solvent is usually a mixed solvent of a low-volatile aromatic glycol ether and an aromatic alcohol or the like and therefore, no significant progress has been achieved other than practicing the above-described operations.
An object of the present invention is to provide a ballpoint ink composition rendered capable of preventing the blobbing phenomenon by, unlike conventional methods, controlling the volatility of ink solvent to prevent extreme drying on the ball surface and control the internal cohesion of the ink.